1. Field of the Invention
This invention relates to a sheet conveying apparatus for conveying sheets in attracting the sheets with electrostatic force and an image forming apparatus having this apparatus.
2. Description of Related Art
As inkjet recording apparatuses advance printing faster these days, a conveying method (electrostatically attracting conveyance method) in use of a conveyance belt having electrodes has been used as a conveyance method for recording media such as paper and plastic sheets.
Referring to drawings, a conventional inkjet recording apparatus having a sheet conveying apparatus of an electrostatic attraction method is described. FIG. 5 is a schematic structural view showing a conventional image forming apparatus; FIG. 6 is a plan view showing a sheet conveying apparatus; FIG. 7 is a front view showing a recording means and the vicinity thereof. The image forming apparatus 50 shown in FIG. 5 includes a recording head 51 for rendering image recording, and a conveyance belt 52 serving as a sheet conveying apparatus adapted for the electrostatic attraction method. The recording head 51 is a liner type having orifices arrayed in a width substantially equal to the sheet width of the sheet to be conveyed and can form images at a high speed in comparison with a recording head of a serial type in which the recording head is mounted on a carriage for scanning movement.
Images may be improperly formed when the head comes in contact with the recording surface to keep the sheet while the sprayed ink is not yet settled right after recording because of high-speed printing. To cope with such a problem, such an apparatus is so designed that a back side opposite to the recording side of the sheet is attracted to the conveyance belt 52 having electrostatically attracting means to convey the sheet without contacting the recording side.
The conveyance belt 52 is an annular stripe shaped member and is wound around a drive roller 58 and a supporting roller 59, thereby conveying sheets by rotatively driving. The electrostatically attracting means is constituted of an electrode group (hereinafter referred to as xe2x80x9ccomb-shaped electrodes 53, 54xe2x80x9d), placed alternatively in a stripe shape as shown in, e.g., FIG. 6, to which different voltages are fed, and conducting blushes 55, 56 on both ends as power supplying means for the conveyance belt 52.
With such a structure, attraction force can be given where one end of the comb-shaped electrodes 53, 54 is connected to the ground level (0 kV) and where the other end is biased to a predetermined voltage (e.g., 3 kV) to create a voltage difference. A surface protection layer 57 is formed on the comb-shaped electrodes 53, 54 as shown in FIG. 7. The conveyance belt 52 while attracting the sheet rotates to convey the sheet, thereby rendering image recording by spraying ink droplets 51a from the recording head 51.
The conventional apparatus, however, requires portions (land portions) to contact the comb-shaped electrodes 53, 54 with the conducting blushes 55, 56 on opposite ends of the sheet in the width direction, and therefore, the conveyance belt 52 has to be formed prescribed size wider than the sheet width. In case where paper jamming occurs under the recording head 51, the conducting blush 55 may interfere with removal of the sheet or sheets and may lower the workability.
It is an object of the invention to provide a compact image forming apparatus which can be recovered from paper jamming or the like with improved workability by changing the arranging method of a power supplying means.
To solve the above problems, a sheet conveying apparatus according to the invention has a structure that including a conveyance belt, on which plural electrodes each fed to a voltage different from that fed to one another are arranged, for conveying a sheet in attracting the sheet with electrostatic force; and power supplying means disposed on an inner side of the conveyance belt for supplying voltage to the electrodes.
According to the structure thus described, because the power supplying means is disposed on an inner side of the conveyance belt, the sheet conveying apparatus can be made compact in comparison with a conventional apparatus that requires to ensure a space for placing the power supplying means on the exterior surface side of the conveyance belt, or namely on an upper side. When a sheet or sheets are removed from the surface of the conveyance belt during paper jamming recovery, the power supplying apparatus does not interfere with the recovery work, so that the workability for such recovery can be improved.